Piston-actuated endoscopic steering system

ABSTRACT

Endoscopic steering apparatus is provided, including an endoscope ( 80 ) having distal ( 82 ) and proximal ( 98 ) ends thereof. In a preferred embodiment, at least one proximal cylinder ( 92 ) is disposed in a vicinity of the proximal end of the endoscope, and at least one proximal piston ( 94 ) is slidably coupled to the at least one proximal cylinder. This piston is typically manually driven. A first distal cylinder ( 88 ) is disposed at the distal end of the endoscope, and a first distal piston ( 90 ) is slidably coupled to the first distal cylinder. A second distal cylinder ( 88 ) is disposed at the distal end of the endoscope, and a second distal piston ( 90 ) is slidably coupled to the second distal cylinder. A first tube ( 86 ) is coupled to the first distal cylinder and to the at least one proximal cylinder, and a second tube ( 86 ) is coupled to the second distal cylinder and to the at least one proximal cylinder. A linkage ( 96 ) is disposed at the distal end of the endoscope and coupled to the first distal piston and to the second distal piston, such that displacement of at least one of the distal pistons causes displacement of the linkage and steering of the distal end of the endoscope.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication 60/395,694 to Raz et al., filed Jul. 11, 2002, entitled,“Piston-actuated endoscopic steering system,” which is assigned to theassignee of the present patent application and is incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates generally to the steering of flexiblemedical devices, and specifically to methods and devices for steeringendoscopes during medical procedures.

BACKGROUND OF THE INVENTION

The use of an endoscope for examining a body cavity is well known in theart. The diagnostic and therapeutic advantages conferred by directexamination of the gastrointestinal tract with a flexible endoscope havemade this method a standard procedure of modern medicine. One of themost common endoscopic procedures is colonoscopy, which is performed fora wide variety of purposes, including diagnosis of cancer, determinationof the source of gastrointestinal bleeding, viewing a site affected byinflammatory bowel disease, removing polyps, and reducing volvulus andintussusception.

While colonoscopy is useful and effective, it is a difficult procedurefor a physician to perform and is painful and occasionally dangerous forthe patient. These problems stem from the need to push and steer thelong, flexible colonoscope through the intestine by pushing it in fromits proximal end, outside the body.

The gastrointestinal tract follows a tortuous path with many sharpturns, sometimes making it difficult or impossible to advance anendoscope to a desired site. A complication of colonoscopy arises whenthe colonoscope perforates the colon, typically at a sharp turn, leadingto spillage of bowel contents into the abdominal cavity, which may leadto infection in the abdominal cavity and the need for emergency surgery.The ability to easily steer an endoscope around sharp turns in thegastrointestinal tract would extend the region of the gastrointestinaltract that is amenable to visualization and/or treatment by theendoscope, greatly enhancing diagnosis and treatment of gastrointestinaldiseases. A number of methods and devices have been proposed for thispurpose, but the region of the gastrointestinal tract that can beaccessed via endoscopes is still limited by the difficulty of navigatingaround sharp bends.

A common means for steering flexible endoscopes is to connect guidedcables or wires to the distal end of the endoscope. Tension is appliedby a physician at the proximal end to the cables or wires, in order toinduce a desired bend at the distal end. The extent to which theendoscope can be steered by this technique is limited by frictionbetween each wire and a sheath surrounding the wire. In particular, if aphysician only needs to overcome a single turn in the gastrointestinaltract, then the force F1 that must be applied at the proximal end inorder to generate a force F2 at the distal end can be approximated asF1=F2*e^(μα), where μ is the coefficient of friction between the wireand the sheath, and α is the effective angle defined by the turn in thegastrointestinal tract. If, as is common, the endoscope travels througha number i of turns α_(i) in the gastrointestinal tract, then the totalforce can increase significantly (and often prohibitively) toF1=F2*e ^(μΣ|α) ^(i) ^(|).

To overcome the effects of friction incurred using wire-based steeringsystems, attempts have been made to introduce hydraulic steering toendoscopes, but none of these have been commercially viable, because allprior art hydraulic steering systems known to the inventor arecomplicated, expensive, bulky and/or require external power or pressuresources, as well as the equipment to manage these sources. Because ofthese drawbacks, only wire-based techniques are currently used forendoscopic steering applications.

U.S. Pat. No. 3,773,034 to Burns et al., which is incorporated herein byreference, describes a method for steering a catheter through a bodypassage by selectively pressurizing fluid conduits that run along theoutside of the catheter. Pressurizing a conduit on one side of thecatheter results in a slight elongation of that side of the catheter,due to elastic deformation, while the length of the opposing side staysconstant, resulting in a curvature of the catheter.

U.S. Pat. No. 4,483,326 to Yamaka et al., which is incorporated hereinby reference, describes a method for steering a flexible endoscope byselectively applying tension to control wires connected to the distalend of the endoscope. Tension is applied to the wires by rotating adrum, about which the wires are wound.

U.S. Pat. No. 4,559,928 to Takayama, which is incorporated herein byreference, describes a method for steering a flexible endoscope byselectively applying tension to control wires connected to the distalend of the endoscope via a motor.

U.S. Pat. No. 4,721,099 to Chikama, U.S. Pat. No. 5,957,863 to Koblishet al., and U.S. Pat. No. 5,297,443 to Wentz, which are incorporatedherein by reference, describe a method for steering a flexible endoscopeby selectively applying tension to control wires connected to the distalend of the endoscope via a hydraulic actuator at the proximal end.

U.S. Pat. No. 4,700,693 to Lia et al. and U.S. Pat. No. 4,790,294 toAllred III et al., which are incorporated herein by reference, describea method for steering a flexible endoscope by selectively applyingtension to control cables connected to the distal end of the endoscope.The control cables run through peripheral bores in axially-aligned flatwashers and spacer beads. The degree of bending can be controlled viathe spacing of the washers and beads, as the beads act as hinges.

U.S. Pat. No. 6,051,008 to Saadat et al. and U.S. Pat. No. 5,188,111 toYates et al., which are incorporated herein by reference, describe amethod for steering a flexible endoscope by selectively heating orcooling strips composed of shape-memory alloy near the distal end of theendoscope.

U.S. Pat. Nos. 4,991,957, 5,048,956 and 5,096,292 to Sakamoto et al.,which are incorporated herein by reference, describe methods forsteering a flexible endoscope by selectively ejecting pressurized fluidfrom one or more jet ports near the distal end of the apparatus.

U.S. Pat. No. 5,577,992 to Chiba et al., U.S. Pat. No. 5,018,506 andU.S. Pat. No. 5,203,319 to Danna et al., U.S. Pat. No. 4,794,912 to Lia,U.S. Pat. No. 5,140,975 to Krauter, and U.S. Pat. No. 4,983,165 toLoiterman, which are incorporated herein by reference, describe methodsfor steering a flexible endoscope by selectively pressurizing balloonsor bladders near the distal end of the endoscope to either push the endof the endoscope in a preferred direction or distort the tip of theendoscope to provide a desired curvature.

U.S. Pat. No. 4,890,602 to Hake, which is incorporated herein byreference, describes methods for steering a flexible endoscope byselectively inflating longitudinal tubes along the endoscope to controlthe curvature of the endoscope. The rigidity of the endoscope is alsocontrolled by the degree of inflation of the longitudinal tubes.

U.S. Pat. No. 5,314,428 to Marotta, which is incorporated herein byreference, describes a method for steering a flexible catheter byselectively pressurizing one or more of multiple channels at the tip ofthe catheter with fluid. Each channel is connected to a piston at theproximal end, which is activated by a rotary mechanical assembly.

U.S. Pat. No. 4,962,751 to Krauter, which is incorporated herein byreference, describes methods for steering endoscopes by using fluiddynamic “muscles,” bladders that contract longitudinally while expandingradially when pressurized, to apply forces to steering wires or cables.The fluid dynamic muscles are placed near the distal end of theendoscope, so that the steering wires or cables can be relatively short.The fluid dynamic muscles are connected to a source of pressurized fluidat the proximal end by a flexible tube.

U.S. Pat. No. 4,832,473 to Ueda and U.S. Pat. No. 5,179,934 to Nagayoshiet al, which are incorporated herein by reference, describe methods forsteering endoscopes by using fluid dynamic muscles in a portion of theendoscope between the distal and proximal ends.

European Patent Application EP 1 036 539 A1 by Matasova, which isincorporated herein by reference, describes a method for steering aflexible catheter by including traction lines connecting the distal andproximal ends of the endoscope. A piston/cylinder connected to vacuumand pressure sources is used to supplement the forces delivered by thetraction lines and aid in steering the endoscope.

A paper entitled, “A Micro Robotic Arm For A Self PropellingColonoscope,” published in Proc. Actuator 98, 6th Int. Conf. on NewActuators, pp. 576-579, June 1998, which is incorporated herein byreference, describes a self-propelling endoscopic system for colonoscopythat comprises a flexible arm, which is controlled by shape memory alloymaterials, to which are attached endoscopic tools. The endoscopic toolsare controlled by either heating/cooling of shape memory alloymechanisms, or by hydraulic means via a piston/cylinder apparatus. Asimple piston/cylinder apparatus is used with a single pressure port onthe cylinder, such that both positive and negative pressures must beused to operate an attached tool. Since only one atmosphere of negativepressure can be applied, forces applied by any tools are limited.Embodiments of the present invention specifically address and overcomethis limitation.

SUMMARY OF THE INVENTION

It is an object of some aspects of the present invention to provide animproved system and method for steering an object within a lumen.

It is a further object of some aspects of the present invention toprovide an improved steering mechanism for steering an endoscope withina body cavity of a patient for purposes of examination, diagnosis, andtreatment.

In preferred embodiments of the present invention, a distal section of aflexible endoscope is advanced through the gastrointestinal tract withthe aid of a steering mechanism near the distal end of the endoscope.The steering mechanism comprises one or more cylinders, each containinga piston, wherein movement of one or more of the pistons actuates rods,wires and/or cables in the steering mechanism to cause turning of thedistal end of the endoscope. Movement of the one or more pistons isachieved by introducing or removing fluid into/from the correspondingcylinders, so as to cause a motion of the piston. The fluid is deliveredfrom the proximal end of the endoscope to the cylinders of the steeringmechanism near the distal end of the endoscope via a closed system offlexible tubes.

Flexible tubes are used such that means for delivering fluid to and fromthe steering mechanism do not impede the advancement of the distal endof the endoscope past curves in the gastrointestinal tract. Theseembodiments of the present invention obviate the need for wires runningthe length of the endoscope to steer the endoscope, thus minimizing someof the difficulties involved with having wires along the entireendoscope, such as friction between the wires and the sleeve, anddifficulty navigating sharp turns in the gastrointestinal tract.

Means for providing fluid to the cylinders in the steering mechanism viathe flexible tubes are preferably located near the proximal end of theendoscope, external to the patient. Thus, there are not necessarily thesame size restrictions as on the steering mechanism, which is near thedistal end of the endoscope and is introduced into the patient'sgastrointestinal tract via the endoscope.

In a preferred embodiment of the present invention, adrive-piston/cylinder system is used to provide pressure to the fluid inthe flexible tubes, so as to drive the steering mechanism. Preferably,the operator uses hand and/or foot movements to displace one or moredrive-pistons in their respective cylinders, resulting in movement offluid into or out of the steering mechanism cylinders, and thus movementof the corresponding pistons and the desired steering of the distal endof the endoscope. Thus, physical forces applied by the operator aredirectly or proportionately applied to steer the endoscope, providingthe operator with a sense of feedback. After a relatively small amountof training and practice, the operator typically learns the amount offorce necessary to apply to a mechanical user-interface device such as ajoystick, in order to turn the distal end of the endoscope a specifiedamount. The physical force required to steer the endoscope is controlledby leveraging or other aspects of the mechanical and/or hydraulic designof the drive mechanism.

In a preferred embodiment of the present invention, each steeringmechanism cylinder comprises one port for introduction or withdrawal offluid so as to move the corresponding piston. A piston divides eachsteering mechanism cylinder into two regions: (a) a fluid-transferregion, comprising a port through which fluid is actively added orwithdrawn, and (b) a passive region, which may be open at one end, orwhich may comprise a spring, or a fixed amount of a compressible fluid.Preferably, the steering mechanism cylinder is aligned with thelongitudinal axis of the endoscope, and the fluid-transfer region iscloser to the distal end of the endoscope than the other region. Thisarrangement is preferred for some applications, because when fluid isadded to the distal end of one of the steering mechanism cylinders, atensile force will develop in wires of the steering mechanism thatconnect the piston to the steerable distal end of the endoscope,eliminating the possibility of buckling due to compressive loads.Mechanical linkages between two or more of the steering mechanismcylinders are preferably designed so as to maintain tensile loads inthese steering mechanism wires when fluid is added to the fluid-transferregion of the cylinder. Alternatively or additionally, one or moresuitably-configured rods are coupled to the steering mechanism cylindersso as to be placed in compression during application or removal of fluidin the fluid-transfer region of the cylinder(s), and to therebyfacilitate steering of the endoscope.

For applications in which the passive region of each steering mechanismcylinder contains a compressible fluid (e.g., air), the fluid typicallyfunctions essentially as a spring, and acts to return the piston to itsequilibrium position. Alternatively or additionally, this regioncomprises a solid spring to assist in returning the piston to itsequilibrium position once no external pressure is applied to thecylinder.

In another preferred embodiment of the present invention, each steeringmechanism cylinder comprises two ports, one on each side of the piston,which are coupled respectively to two fluid-transfer regions of thecylinder, into or out of which fluid is actively added or removed.Flexible tubes convey hydraulic pressure from the proximal end of theendoscope to each port. Movement of a given piston is initiatedresponsive to the difference in the fluid pressure on opposing sides ofthe piston. By regulating the pressure on each side of the piston,accurate control of the force delivered by the piston to the steeringmechanism linkage is achieved. Inclusion of input/output ports in eachregion of the steering mechanism cylinders allows for the use ofsubstantially incompressible fluids, e.g., water, to drive the steeringmechanism.

There is therefore provided, in accordance with a preferred embodimentof the present invention, endoscopic steering apparatus, including:

an endoscope, having distal and proximal ends thereof;

at least one proximal cylinder, disposed in a vicinity of the proximalend of the endoscope;

at least one proximal piston, slidably coupled to the at least oneproximal cylinder;

a first distal cylinder, disposed at the distal end of the endoscope;

a first distal piston, slidably coupled to the first distal cylinder;

a second distal cylinder, disposed at the distal end of the endoscope;

a second distal piston, slidably coupled to the second distal cylinder;

a first tube, coupled to the first distal cylinder and to the at leastone proximal cylinder;

a second tube, coupled to the second distal cylinder and to the at leastone proximal cylinder; and

a linkage disposed at the distal end of the endoscope and coupled to thefirst distal piston and to the second distal piston, such thatdisplacement of at least one of the distal pistons causes displacementof the linkage and steering of the distal end of the endoscope.

The proximal piston is typically manually driven, but may also be drivenby an actuator, e.g., an electromechanical actuator.

In a preferred embodiment, the apparatus is configured such that:

-   -   the at least one proximal cylinder includes respective first and        second proximal cylinders,    -   the at least one proximal piston includes respective first and        second proximal pistons, slidably coupled to the first and        second proximal cylinders, respectively,    -   the first tube is coupled to the first distal cylinder and to        the first proximal cylinder, and    -   the second tube is coupled to the second distal cylinder and to        the second proximal cylinder.

Alternatively or additionally, the apparatus is configured such that:

-   -   the at least one proximal cylinder includes a single proximal        cylinder,    -   the at least one proximal piston includes a single proximal        piston, slidably coupled to the single proximal cylinder,    -   the single proximal cylinder has a proximal port and a distal        port, disposed at respective ends of the single proximal        cylinder, and    -   the first and second tubes are coupled to the single proximal        piston at the proximal and distal ports, respectively.

For some applications, the linkage includes a flexible element, disposedin the endoscope such that tension in the element translates adisplacement of one of the distal pistons into a change in angulardisposition of the distal end of the endoscope. Alternatively oradditionally, the linkage includes an element, disposed in the endoscopesuch that compression in the element translates a displacement of one ofthe distal pistons into a change in angular disposition of the distalend of the endoscope.

Preferably, the apparatus includes a mechanical user-interface device,which is coupled to the at least one proximal cylinder so as tomechanically transduce a force generated by a user of the steeringapparatus into a motion of the at least one proximal piston.

There is also provided, in accordance with a preferred embodiment of thepresent invention, endoscopic steering apparatus, including:

an endoscope, having distal and proximal ends thereof, the distal endincluding a forward section and a rear section flexibly coupled to theforward section;

a distal cylinder, disposed at the rear section of the distal end of theendoscope;

a distal piston, slidably coupled to the distal cylinder and coupled tothe forward section of the distal end of the endoscope;

a proximal cylinder, disposed in a vicinity of the proximal end of theendoscope;

a manually-driven proximal piston, slidably coupled to the proximalcylinder; and

a tube, coupled between the distal cylinder and the proximal cylinder,such that displacement of the proximal piston generates a pressure inthe tube capable of displacing the distal piston and rotating theforward section with respect to the rear section.

Preferably, the distal cylinder has a distal port, distal to the distalpiston, in communication with the tube, such that positive pressure inthe tube responsive to displacement of the proximal piston inducesproximal motion of the distal piston.

Further preferably, the apparatus is configured such that:

-   -   the proximal cylinder has a first port, which is in        communication with a first face of the proximal piston, and a        second port, which is in communication with a second face of the        proximal piston,    -   the tube is coupled to the proximal cylinder at the first port,        so as to be in communication with the first face of the proximal        piston,    -   the distal cylinder has a proximal port, proximal to the distal        piston, and    -   the apparatus includes an additional tube having distal and        proximal ends thereof, the additional tube being in        communication at the distal end thereof with the proximal port        of the distal cylinder, and being in communication at the        proximal end thereof with the second port of the proximal        cylinder,    -   whereby positive pressure in the additional tube responsive to        displacement of the proximal piston induces distal motion of the        distal piston.

For some applications, the apparatus is configured such that:

-   -   the apparatus includes an additional proximal cylinder, disposed        in a vicinity of the proximal end of the endoscope,    -   the apparatus includes an additional manually-driven proximal        piston, slidably coupled to the additional proximal cylinder,    -   the distal cylinder has a proximal port, proximal to the distal        piston, and    -   the apparatus includes an additional tube, coupled between the        proximal port of the distal cylinder and the additional proximal        cylinder,    -   whereby positive pressure in the additional tube responsive to        displacement of the additional proximal piston induces distal        motion of the distal piston.

The present invention will be more fully understood from the followingdetailed description of the preferred embodiments thereof, takentogether with the drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic, sectional drawings of an endoscopecomprising a hydraulic steering mechanism, in two respective statesthereof, according to a preferred embodiment of the present invention;

FIG. 2 is a schematic, sectional drawing of an endoscope comprising ahydraulic steering mechanism, according to another preferred embodimentof the present invention;

FIG. 3 is a schematic, sectional drawing of an endoscope comprising ahydraulic steering mechanism, according to yet another preferredembodiment of the present invention; and

FIG. 4 is a schematic, sectional drawing of an endoscope comprising ahydraulic steering mechanism, according to still another preferredembodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to FIGS. 1A and 1B, which are schematic sectionaldrawings of a flexible endoscope 80 comprising a hydraulic steeringmechanism, in accordance with a preferred embodiment of the presentinvention. The endoscope is shown in a first, straight, state (FIG. 1A),as well as in a second state (FIG. 1B) during steering of the endoscope.Endoscope 80 comprises a distal portion 82, which is advanced into thegastrointestinal tract of a patient, and a proximal portion 98, part ofwhich remains external to the patient and is accessible to the operatorof the endoscope. Typically, a probe 97 is disposed near the tip ofendocope 80, for diagnosis and/or treatment of the patient. In apreferred embodiment, probe 97 comprises a camera for examining theinterior of the gastrointestinal tract. Alternatively or additionally,probe 97 comprises a tool, such as a biopsy device or a treatmentdevice.

Distal portion 82 preferably comprises a forward section 74 coupled toarticulate at a joint 76 with a rear section 78. Means for facilitatingsteering of the endoscope are located in rear section 78, and preferablycomprise a plurality of cylinders 88, each of which comprises a piston90. It is to be understood that a universal joint or a variety of otherjoint structures known in the art may be used for coupling forwardsection 74 to rear section 78, and that the scope of the presentinvention is not limited to a joint such as that shown in the figures.For clarity, FIGS. 1A and 1B show only two cylinders 88, disposed at 180degrees with respect to the central axis of the endoscope, in order toallow for turning of the endoscope in an arc. However, it is to beunderstood that the scope of the present invention includes the use ofdevices with more than two cylinders disposed at respective positionsaround the central axis, so as to allow the operator to turn theendoscope in any direction. Alternatively, two cylinders may be placedon the same side of the central axis, e.g., at 12 o'clock and 3 o'clock,and controlled simultaneously to produce x-axis and y-axis motion.Further alternatively, only one cylinder may be located in rear section78, and coupled to facilitate the steering of forward section 74.

Each piston 90 is preferably coupled to one end of respective elements84. The opposite ends of elements 84 are coupled to respective portionsof a linkage 96 in forward section 74. The linkage is preferably coupledto endoscope 80 near the tip of distal portion 82. Movement of pistons90 is thus translated to linkage 96, and differential motion of pistons90 causes rotation of linkage 96 and turning of the distal end of theendoscope at joint 76 (FIG. 1B). As appropriate, linkage 96 may beshaped like a ring. Alternatively, the linkage comprises one or moreconnection points of elements 84 to the forward section. Seals 99 arepreferably provided to facilitate the movement of elements 84 whileinhibiting leakage of fluid from cylinders 88. Those of skill in the artwill appreciate that there are a variety of means for coupling elements84 in order to produce desired motions of endoscope 80. For example,elements 84 may be rigid or flexible, and coupled to the other elementsof distal portion 82 so as to be placed in compression or tensionresponsive to the pressure in cylinders 88.

Movement of pistons 90 is driven by fluid delivered to or withdrawn fromcylinders 88 via flexible tubes 86. It is to be understood in thecontext of the present patent application and in the claims that theterm “fluid” is meant to include a liquid and/or a gas. Preferably, eachcylinder 88 is aligned parallel to the longitudinal axis of theendoscope, and fluid is delivered to or withdrawn from a port 89 nearthe distal end of the cylinder. Each cylinder is thus divided into twosections by piston 90: (a) a fluid transfer section 91, closer to thedistal end of the endoscope, where fluid is delivered or withdrawn, and(b) a passive section 93, closer to the proximal end of the endoscope.

Advantageously, linkage 96 is preferably designed to operate responsiveto tension (or compression) in one of elements 84, whereby applyingpositive pressure to one piston 90 tends to force that pistonproximally. This minimizes the need for suction and the potentialproblems with collapse of flexible tubes 86. Additionally, suction as ameans for generating useful motion of the endoscope is generally limitedto one atmosphere, while positive pressure can exceed one atmosphere.Experiments performed using the principles of the present invention havegenerated positive pressures of 50 atmospheres at the distal end, usingonly the force easily generated by hand, applied to the simple andinexpensive apparatus preferred in accordance with these embodiments ofthe present invention. It is emphasized that prior art systems forhydraulic endoscopic steering generally require complicated andexpensive apparatus, which utilize pumps and pressure-regulationapparatus or other powered equipment to operate.

Typically, passive section 93 of cylinder 88 comprises a venting port101, which allows fluid to enter or leave the cylinder as piston 90 isdisplaced. For some applications, passive section 93 of cylinder 88 issealed, and encloses a compressible fluid such as air, which acts like aspring when piston 90 is displaced, tending to return the piston to itsequilibrium position. In a preferred embodiment of the presentinvention, the passive section of cylinder 88 comprises an elasticelement such as a spring (not shown), which returns piston 90 in itsequilibrium position.

Fluid is delivered to or withdrawn from one of cylinders 88 responsiveto the operation of pressure apparatus 95, preferably comprising, tocontrol each cylinder 88, a drive-piston 94 in a drive cylinder 92. Eachdrive-piston 94 is preferably coupled to the respective cylinder 88 byone of flexible tubes 86. Applying a force to drive-piston 94pressurizes the fluid in drive cylinder 92. This pressure is transmittedthrough the fluid in tube 86 and in cylinder 88, and comes to act onpiston 90, to cause steering of endoscope 80 as described hereinabove.The ratio of the driving force applied to drive-piston 94 to thepressure force received by piston 90 is generally proportional to thearea ratio of the two piston faces. Thus, fine control of the steeringof endoscope 80 can be achieved by decreasing the area of piston 94relative to the area of piston 90. In this manner, operator-inducedmotions of piston 94 can be leveraged to yield fine motions of piston90. The force required to steer the endoscope can be selected by sizingdrive-piston 94 and piston 90 appropriately.

In some preferred embodiments of the present invention, a mechanicallinkage, such as a joystick 102 mechanically coupled to pistons 94, isused to actuate drive-pistons 94 to make steering the endoscope moreergonomic. For applications in which more cylinders are used at thedistal and/or proximal ends of endoscope 80, appropriate changes in thelinkage are provided, so as to facilitate greater ease of use for theoperator.

In a preferred embodiment of the present invention, endoscope 80 ispropelled through the gastrointestinal tract using methods and apparatusdescribed in PCT Patent Publication WO 02/19886, entitled “Double sleeveendoscope,” which is assigned to the assignee of the present patentapplication and is incorporated herein by reference. As described inthat application, inflation by compressed air of a dual-sleeved,extendable tube that is attached to the distal portion of an endoscopepushes the distal portion through the gastrointestinal tract of apatient without the use of wires, which are commonly used in the priorart. The absence of wires running the length of the endoscope leads to amore flexible endoscope, which does not risk buckling of members incompression, and which reduces the risk of injuring the intestinethrough which the endoscope travels. Preferably, use of the inflatingsleeve in combination with the methods and apparatus of the presentpatent application allows the operator to propel and steer the endoscopearound turns in the gastrointestinal tract.

FIG. 2 is a schematic sectional drawing of a flexible endoscope 50,representing another preferred embodiment of the present invention.Preferably, endoscope 50 comprises a plurality of pistons and cylinders,generally as used in pressure apparatus 95 of FIGS. 1A and 1B, exceptwith differences as described herein. The hydraulic steering mechanismof endoscope 50 differs from that of endoscope 80 in that fluid pressureis supplied to both faces of pistons 90 so as to provide a net forcewhich produces motion of the pistons, while fluid pressure is onlysupplied to one side of pistons 90 in endoscope 80.

Each of two cylinders 52 in distal portion 82 of endoscope 50 is coupledto two fluid supply tubes coming from pressure apparatus 81: (a) adistal fluid supply tube 86 coupled to the distal end of cylinder 92,and (b) a proximal fluid supply tube 72, coupled to a port 103 on theproximal end of cylinder 92. With this closed-loop arrangement, it ispossible to precisely control the net force on each piston 90, and toaccurately steer the endoscope. Either a compressible fluid (e.g., air)or a substantially-incompressible fluid (e.g., water) is used to drivepistons 90.

It is to be understood that four cylinders are not required to achievethe benefits of the present invention. Closed-loop steering mechanismssimilar to that shown in FIG. 2, but having fewer cylinders may beparticularly useful for some applications. In a preferred embodiment, asteering mechanism is provided comprising two proximal cylinders and onedistal cylinder, each of the proximal cylinders coupled by a flexibletube to apply positive pressure to opposing faces of a piston in thedistal cylinder. Alternatively, a steering mechanism comprising twodistal cylinders and one proximal cylinder is provided, in which tubescoupled to opposing ends of the proximal cylinder convey positivepressure to one or the other of the distal cylinders, responsive to thedirection of motion of a piston in the proximal cylinder.

FIG. 3 is a schematic sectional drawing of a flexible endoscope 100representing still another preferred embodiment of the presentinvention. Endoscope 100 functions generally similarly to endoscope 80described hereinabove with reference to FIGS. 1A and 1B, but differs insome aspects of the steering mechanism. For endoscope 80, pistons 90 areindirectly coupled through elements 84 and linkage 96, while forendoscope 100 a substantially inextensible belt 104 directly couplesopposing pairs of pistons 90. Pistons 90 are thus constricted to moveequal distances in opposite directions. It is to be understood thatwhile FIG. 4 presents only two cylinders 88, the scope of the presentinvention includes other embodiments comprising an even number ofcylinders 88, where pairs of opposing cylinders are coupled by a belt.

Belt 104 preferably runs over a gear 118 or analogous mechanism, whichis coupled to a linkage 116, such that rotation of the gear due tomovement of belt 104 causes rotation of the linkage and the desiredturning of the distal end of the endoscope.

FIG. 4 is a schematic sectional drawing of a flexible endoscope 120representing yet another preferred embodiment of the present invention.Endoscope 120 functions generally similarly to endoscope 80 describedhereinabove with reference to FIGS. 1A and 1B, but differs in someaspects of the pressure apparatus. Whereas pressure apparatus 95 ofendoscope 80 comprises two proximal piston/cylinders, one to drive eachof the two distal pistons, a pressure apparatus 83 of endoscope 120comprises only 1 proximal piston/cylinder device. A piston 94 dividesthe cylinder into a distal portion 92 and a proximal portion 118, suchthat distal movement of piston 94 simultaneously forces fluid out ofdistal portion 92 and into proximal portion 118. Distal portion 92 andproximal portion 118 are each coupled to a separate cylinder 88 byseparate tubes 86, so as to steer the endoscope as discussed hereinabovewith reference to FIGS. 1A and 1B.

In another preferred embodiment, only one distal cylinder 88 is used tosteer the endoscope, resulting in a system comprising one distalcylinder and one proximal cylinder.

It will be appreciated that the preferred embodiments described aboveare cited by way of example, and that the present invention is notlimited to what has been particularly shown and described hereinabove.Rather, the scope of the present invention includes both combinationsand subcombinations of the various features described hereinabove, aswell as variations and modifications thereof which would occur topersons skilled in the art upon reading the foregoing description andwhich are not disclosed in the prior art.

1. Endoscopic steering apparatus, comprising: an endoscope, havingdistal and proximal ends thereof; at least one proximal cylinder,disposed in a vicinity of the proximal end of the endoscope; at leastone proximal piston, slidably coupled to the at least one proximalcylinder; a first distal cylinder, disposed at the distal end of theendoscope; a first distal piston, slidably coupled to the first distalcylinder; a second distal cylinder, disposed at the distal end of theendoscope; a second distal piston, slidably coupled to the second distalcylinder; a first tube, coupled to the first distal cylinder and to theat least one proximal cylinder; a second tube, coupled to the seconddistal cylinder and to the at least one proximal cylinder; and a linkagedisposed at the distal end of the endoscope and coupled to the firstdistal piston and to the second distal piston, such that displacement ofat least one of the distal pistons causes displacement of the linkageand steering of the distal end of the endoscope.
 2. Apparatus accordingto claim 1, wherein the at least one proximal piston is adapted to bemanually driven.
 3. Apparatus according to claim 1, wherein the at leastone proximal piston is adapted to be power driven.
 4. Apparatusaccording to claim 1, wherein the at least one proximal cylindercomprises respective first and second proximal cylinders, wherein the atleast one proximal piston comprises respective first and second proximalpistons, slidably coupled to the first and second proximal cylinders,respectively, wherein the first tube is coupled to the first distalcylinder and to the first proximal cylinder, and wherein the second tubeis coupled to the second distal cylinder and to the second proximalcylinder.
 5. Apparatus according to claim 1, wherein the at least oneproximal cylinder comprises a single proximal cylinder, wherein the atleast one proximal piston comprises a single proximal piston, slidablycoupled to the single proximal cylinder, wherein the single proximalcylinder has a proximal port and a distal port, disposed at respectiveends of the single proximal cylinder, and wherein the first and secondtubes are coupled to the single proximal piston at the proximal anddistal ports, respectively.
 6. Apparatus according to claim 1, whereinthe linkage comprises a flexible element, disposed in the endoscope suchthat tension in the element translates a displacement of one of thedistal pistons into a change in angular disposition of the distal end ofthe endoscope.
 7. Apparatus according to claim 1, wherein the linkagecomprises an element, disposed in the endoscope such that compression inthe element translates a displacement of one of the distal pistons intoa change in angular disposition of the distal end of the endoscope. 8.Apparatus according to any one of claims 1, wherein the linkage isconfigured so as to translate a displacement of one of the distalpistons into a displacement of the other one of the distal pistons. 9.Apparatus according to any one of claims 1, and comprising a mechanicaluser-interface device, which is coupled to the at least one proximalcylinder so as to mechanically transduce a force generated by a user ofthe steering apparatus into a motion of the at least one proximalpiston.
 10. Endoscopic steering apparatus, comprising: an endoscope,having distal and proximal ends thereof, the distal end comprising aforward section and a rear section flexibly coupled to the forwardsection; a distal cylinder, disposed at the rear section of the distalend of the endoscope; a distal piston, slidably coupled to the distalcylinder and coupled to the forward section of the distal end of theendoscope; a proximal cylinder, disposed in a vicinity of the proximalend of the endoscope; a proximal piston, slidably coupled to theproximal cylinder; and a tube, coupled between the distal cylinder andthe proximal cylinder, such that displacement of the proximal pistongenerates a pressure in the tube capable of displacing the distal pistonand rotating the forward section with respect to the rear section. 11.Apparatus according to claim 10, wherein the proximal piston is adaptedto be manually driven.
 12. Apparatus according to claim 10, wherein theproximal piston is adapted to be power driven.
 13. Apparatus accordingto claim 10, and comprising a mechanical user-interface device, which iscoupled to the proximal cylinder so as to mechanically transduce a forcegenerated by a user of the steering apparatus into a motion of theproximal piston.
 14. Apparatus according to claim 10, wherein the distalcylinder has a distal port, distal to the distal piston, incommunication with the tube, such that positive pressure in the tuberesponsive to displacement of the proximal piston induces proximalmotion of the distal piston.
 15. Apparatus according to claim 14,wherein the proximal cylinder has a first port, which is incommunication with a first face of the proximal piston, and a secondport, which is in communication with a second face of the proximalpiston, wherein the tube is coupled to the proximal cylinder at thefirst port, so as to be in communication with the first face of theproximal piston, wherein the distal cylinder has a proximal port,proximal to the distal piston, wherein the apparatus comprises anadditional tube having distal and proximal ends thereof, the additionaltube being in communication at the distal end thereof with the proximalport of the distal cylinder, and being in communication at the proximalend thereof with the second port of the proximal cylinder, such thatpositive pressure in the additional tube responsive to displacement ofthe proximal piston induces distal motion of the distal piston. 16.Apparatus according to claim 14, wherein the apparatus comprises anadditional proximal cylinder, disposed in a vicinity of the proximal endof the endoscope, wherein the apparatus comprises an additionalmanually-driven proximal piston, slidably coupled to the additionalproximal cylinder, wherein the distal cylinder has a proximal port,proximal to the distal piston, wherein the apparatus comprises anadditional tube, coupled between the proximal port of the distalcylinder and the additional proximal cylinder, such that positivepressure in the additional tube responsive to displacement of theadditional proximal piston induces distal motion of the distal piston.